Eigen
3.3.4

Holds information about the various numeric (i.e. scalar) types allowed by Eigen.
T  the numeric type at hand 
This class stores enums, typedefs and static methods giving information about a numeric type.
The provided data consists of:
Real
, giving the "real part" type of T. If T is already real, then Real
is just a typedef to T. If T is std::complex<U>
then Real
is a typedef to U. NonInteger
, giving the type that should be used for operations producing nonintegral values, such as quotients, square roots, etc. If T is a floatingpoint type, then this typedef just gives T again. Note however that many Eigen functions such as internal::sqrt simply refuse to take integers. Outside of a few cases, Eigen doesn't do automatic type promotion. Thus, this typedef is only intended as a helper for code that needs to explicitly promote types. Literal
giving the type to use for numeric literals such as "2" or "0.5". For instance, for std::complex<U>
, Literal is defined as U
. Of course, this type must be fully compatible with T. In doubt, just use T here. std::complex
type, and to 0 otherwise. 1
if T is an integer type such as int
, and to 0
otherwise. 1
if T is a signed type and to 0 if T is unsigned. 1
if the constructor of the numeric type T must be called, and to 0 if it is safe not to call it. Default is 0 if T is an arithmetic type, and 1 otherwise. Inherits Eigen::GenericNumTraits< T >.